Bias circuits are widely employed in analog or mixed signal electronic circuitry to set operating conditions by establishing a predetermined voltage at a given node. Typically, maintaining a bias node at a desired voltage consumes power. Therefore, bias circuits are often disabled in low-power or power-down operating states. A bias circuit may also require a length of time to generate a steady state voltage at the bias node, and the length of time may be related to power consumption and noise filtering.
On-chip regulators represent a specific class of bias circuits that typically are used to generate a non-rail supply voltage for other circuits. Regulators generally provide power and are heavily bypassed, exacerbating the maintenance power issue as well as the length of time required to reach steady state.